Contact lens manufacturing method

ABSTRACT

In manufacturing a contact lens, a contact lens mould arrangement in which the engagement between the mould halves is unconstrained and at least one mould half is sufficiently pliable or flexible that during the curing of the contact lens composition at one mold half may move or flex relative to the other to define a post-cure mould cavity of smaller volume than the precure mould cavity and during which the curvatures of the first and/or second mould surfaces are allowed to change provides a significantly more efficient manufacturing process and enables one mould half to be readily utilized as a blister cup for contact lens packaging.

FIELD OF THE INVENTION

This invention pertains generally to the field of contact lenses,contact lens manufacturing and contact lens packaging. It furtherrelates to an apparatus, system and method for the manufacture ofcontact lenses, to a contact lens and to packaged contact lens and to amethod of packaging a contact lens.

BACKGROUND OF THE INVENTION

Three basic manufacturing techniques are used in the manufacture of softcontact lenses. These are generally referred to as lathing (cutting bothlens surfaces and edge on a pre-polymerised ‘button’), spin casting(using a single concave mould piece to form the front surface of thelens) and cast moulding (using a concave mould piece to form the frontsurface of the lens and a second convex mould pieces to form the backsurface of the lens).

Lathing is a suitable process where there is a low batch size and a widevariety of lens powers and/or shapes required e.g. for toric lensmanufacture. Spin casting is a suitable process for higher batch sizes,however, the ‘open’ surface not being in contact with a mould will beparabolic this being a ‘compromise’ profile to the generally sphericalprofile of the cornea. Cast moulding is a suitably process for very highvolume manufacture and facilitates the precise profiling of both thefront (by the concave mould surface) of the lens and back surface (bythe convex mould surface) of the lens e.g. creating a bi-curve or even atri-curve profile for optimum cornea fit.

There are also three basic contact lens packaging systems: a glass vialwith bung and metal clip closure; a plastic ‘mould-cup’ with metallisedfoil seal; and an integrated plastic ‘mould-cup’ where one of the mouldpieces used to form a cast lens is also used as the packing containergenerally sealed with metallised foil.

The health-care benefits of frequent lens replacement, e.g. monthly,bi-weekly or daily replacement, necessitate the lowest cost of lensmanufacture and packaging. For example, the cost of vial packagingrenders this system inappropriate on cost grounds for any frequentreplacement modality of lens wear. Daily-disposable contact lenses areincreasingly recognised as providing the healthiest modality of contactlens wear but the wearer's requirement of up to 730 contact lenses peryear requires extremely low unit cost whilst ensuring high quality lensmanufacture and high levels of on-eye comfort and visual acuity.

The optimum combination for meeting these stringent requirements wouldbe the use of a cast-moulding process incorporating the use of one ofthe mould-pieces (either the concave or convex moulding) to form thelens-cup package.

In cast-moulding of soft contact lenses, which typically comprisescuring a curable solution (of, typically, polymerisable monomers) in alens-forming cavity formed between two mould halves, the commonchallenges include controlling the power of the contact lens beingproduced and edge formation. If the edge-formation is inconsistent, itmay require cutting. If the edge formed is too discrete, it may causediscomfort for the user. A further problem in the cast-moulding ofcontact lenses is how to deal with monomer ‘shrinkage’, the inevitablereduction in volume in the curing stage. The monomer materials undergovolumetric shrinkage of at least 10% and typically between 10 and 20%.Failure to properly compensate for this shrinkage will result inunacceptably high wastage rates and/or poor quality products containingvoids or bubbles.

There are several approaches that have been developed in thecast-moulding of contact lenses designed to enhance contact lensmanufacture and in some cases to overcome one or more of the aboveproblems.

GB-A-2006091 describes a method of manufacturing contact lenses bycuring (or gelling) a contact lens-forming solution in a lens shapedspace formed between a concave mould and a convex mould. This method ischaracterised by the mould cavity being an open mould and byover-filling the mould cavity with solution so as to form a reservoir ofsolution which can seep back into the mould cavity to allow forvolumetric shrinkage during the curing (or gelling) process. Aparticular problem with this method, however, is that fluid within thechannel (at the edges of the mould cavity), where fluid from thereservoir is intended to flow into the mould cavity during curing, tendsto cure more rapidly (due to the confined volume) as compared with themain body of the lens cavity. A further problem is that post-curing, itis necessary to cut the cured ‘reservoir’ ring from the mould, or whereit is selectively cured to cut or polish imperfectly formed edges.Rigid, inflexible materials, such as glass, are preferred for use as themould halves.

WO-A-87/04390 describes a polyolefin mould for casting contact lenses. Amould cavity in which a monomer composition is placed for formation of acontact lens is formed between plastic male and female mould halveswhich cooperate by sliding fit and reach a final engagement positionwhen a rigid (non-flexible) shoulder on one mould half (typically thefemale) engages with the other mould half to form a seal. The point ofengagement of the rigid shoulder with the other mould half (preferably arigid engagement) defines the radial diameter of the lens to be formed.At least one mould half, typically the male mould half, is formed with adiaphragm portion in which the material is sufficiently thin andflexible as to move toward the other mould half under the forcesgenerated by the monomer shrinkage during curing. Such diaphragmbehaviour of at least one mould half thereby compensates for thevolumetric shrinkage during curing. The diaphragm behaviour is intendedto avoid bubbles and voids in the resultant contact lenses. The rigidshoulder is preferably formed on the female mould half and preferablywith a slight return, to ensure that the moulded lens remains in thefemale mould half when the mould halves are separated. WO-A-87/04390further discloses that the female mould half retaining the cured lensmay be used as a package for the hydrated lens by hydrating the lens andsealing a lid to the flange of the female mould half. A particulardisadvantage of this system is that the diaphragm portion which flexesduring curing is difficult to form in a manner which gives consistentcurvature in the lenses (or to ensure that cavitation and bubbles in thelens are avoided). Further, in providing a return on a non-flexibleshoulder, removal of the lens from the female mould half is difficult,even if hydrated in situ. The proposed mould arrangement is bulky (inorder to ensure that a slide fit engagement can be achieved and toprovide internal volume for later processing), which leads tosignificant material loss (in the male half that is disposed of) andresultant bulky packaging of contact lens.

US-B-5143660 is an alternative arrangement for providing a mould half asa contact lens package and which arrangement also utilises diaphragmbehaviour of the mould surfaces to compensate for monomer shrinkageduring curing. In US-B-5143660, the two mould halves cooperate to sealagainst a rigid shoulder by a sliding fit which seal defines a radialdiameter of the lens. The curing stage is carried out atsuperatmospheric pressure to ensure that even deflection of thediaphragm surface (typically of each mould half) occurs in order toproduce lenses of consistent and even curvature. The male mould halfsurface is formed with greater surface energy so as to allow the lens toremain on the male mould half after separation of the mould halves. Themale mould half is provided with an annular wall (which is involved inthe sliding fit) whereby a lid may be applied to the rim of the annularwall to form a package in which the lens is provided on the convexinternal surface of the package, thereby presenting the lens in a mannerthat it can be removed by the user without touching the eye-contactingsurface of the lens. Disadvantages of this system include the precisionof manufacture necessary to ensure sealed sliding fit and diaphragmbehaviour, the increased complexity of requiring superatmosphericpressure, the excess material required to provide the slide-fitengagement (and non-optical) portions of the mould half and the factthat the convention in contact lens use is for the user to be presentedwith a lens concave surface up.

EP-A-0383425 describes a contact lens mould arrangement having male andfemale mould halves in sliding fit cooperation in which the male mouldhalf is provided with a shoulder that engages a cylindrical orfrusto-conical portion of the female mould half adjacent the anteriorlens surface-forming mould surface. During polymerisation, the malemould half may move toward the female mould half from its pre-engagementposition defined by engagement of mating surfaces (flanges) formed onthe distal edges of the cylindrical walls as a result of a hingingeffect of the male mould half at the shoulder junction. Thereby thevolumetric shrinkage may be compensated by the male mould half movingslightly toward the female mould half as a result of this lever effect.

Several documents describe another form of mould arrangement in whichthe curvature of the lens forming surfaces of the mould halves remainsconstant but the cavity volume (and radial diameter) changes during thecuring by providing an annular flexible lip on the male or female mouldhalf at the extremity of lens-forming cavity, which flexing of the lipallows the two mould halves to move closer together to compensate formonomer shrinkage. One example is GB-A-1575694 in which apiston-cylinder slide fit arrangement of rigid mould halves is providedto define a mould cavity, the edge region defined by the engagement of aflexible rim formed on the male or female mould half with the othermould half. During curing, the lip flexes (typically inward) allowingthe mould halves to move closer to compensate for monomer shrinkage.WO-A-2004/076160 provides a similar slide-fit arrangement whereby aflexible annular lip is provided on a female mould half which engageswith an annular abutment section of a male mould half thereby definingthe edge of the contact lens. During curing, the lip may flex radiallyoutwards along the abutment surface thereby increasing the radialdimension of the lens forming cavity whilst the two mould halves aredrawn together. A particular disadvantage of the flexible liparrangement is that the flexible lip can affect the seal resulting inreject lenses and the edge portions of resulting lenses tend to beinconsistent and in need cutting or polishing. Further, to ensuremisalignment does not occur, the cylinder-piston arrangement of mouldhalves must be manufactured with a good deal of precision to ensureclose and replicable fit.

The prior art thus suffers from disadvantages mentioned, which typicallyinclude one or more of inconsistency of lens edge-forming, reliabilityand consistency of lens curvature, complexity of manufacturing,requirements for precision in non-optical portions of mould-halves,degree of material waste and unsuitability for use of the lens-formingmould half in packaging.

The present inventors have found that a fundamentally new approach tocast moulding of contact lenses allows them to overcome many of theabove problems, to utilise more efficient manufacturing processes and toeffectively and efficiently utilise a mould half as a blister in contactlens packaging.

PROBLEM TO BE SOLVED BY THE INVENTION

There remains a need for improvements in contact lens manufacture whichaddress one or more of the aforementioned problems.

It is an object of this invention to provide a method of manufacturingcontact lenses that provides increased efficiency in manufacturingcombined with optimization of lens design.

It is a further object of this invention to provide a method ofmanufacturing a contact lens that enables a mould half to be utilized incontact lens packaging.

It is a still further object of the invention to provide a mould halfthat is useful for efficient contact lens manufacture and for use as acompact and user friendly contact lens pack.

It is still further an object of the invention to provide a method ofmanufacturing and producing a contact lens having the required opticalproperties at low unit cost.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, there is provided amethod for the manufacture of a contact lens, the method comprisingproviding a first, concave, mould-half having a first concave mouldsurface to correspond with a convex surface of the contact lens;providing a second, convex, mould-half having a second convex mouldsurface to correspond with a concave surface of the contact lens, saidsecond mould half configured to engage with the first mould-half todefine a first, pre-cure, mould cavity therebetween, which mould cavityis defined by the first, concave, mould surface and second, convex,mould surface said first and second mould surfaces having respectivecurvatures to correspond with a pre-determined lens power/curvature andwherein the first or second mould surface is defined by an annular ridgeformed on the respective mould half; disposing into the mould cavity acurable lens-forming fluid composition; curing said composition to forma pre-hydrated lens; and separating the first and second mould halves,characterized in that the engagement between the mould halves isunconstrained and at least one mould half is sufficiently pliable suchthat during the curing of said composition the first and/or second mouldhalves move relative to one another and/or flex such as to definebetween the first and second mould surfaces a second, post-cure, mouldcavity, which second post-cure mould cavity defines a smaller volumethan said first pre-cure mould cavity.

In a second aspect of the invention, there is provided a method for themanufacture of a contact lens, the method comprising providing a first,concave, mould-half having a first concave mould surface to correspondwith a convex surface of the contact lens; providing a second, convex,mould-half having a second convex mould surface to correspond with aconcave surface of the contact lens, said second mould half configuredto engage with the first mould-half to define a first, pre-cure, mouldcavity therebetween, which mould cavity is defined by the first,concave, mould surface and second, convex, mould surface said first andsecond mould surfaces having respective curvatures to correspond with apre-determined lens power/curvature and wherein the first or secondmould surface is defined by an annular ridge formed on the respectivemould half; disposing into the mould cavity a curable lens-forming fluidcomposition; curing said composition to form a pre-hydrated lens; andseparating the first and second mould halves, characterized in that atleast the first mould half is formed of a material sufficiently pliableunder curing conditions that during curing, the radial dimension definedby the diameter of the annular ridge changes to accommodate thevolumetric reduction of lens-forming composition due to curing.

In a third aspect of the invention, there is provided a female mouldhalf that has an annular ridge and that is sufficiently pliable thatunder curing conditions (to cure a contact lens-forming curable fluidcomposition) and in contiguous contact via the annular ridge with a malemould half, the female mould half may flex, optionally in concert withthe male mould half, to accommodate any shrinkage of the composition.

In a fourth aspect of the invention, there is provided the use of afemale mould half as defined above as a blister cup.

In a fifth aspect of the invention, there is provided a packaged contactlens comprising a blister cup containing a hydrated contact lens ofpre-determined hydrated curvature, a saline solution, and a foil coversealed to a rim of the blister cup, the blister cup comprising anannular ridge (or protrusion) on its interior surface and a curvedoptical portion radially inwards from said annular ridge said curvedportion having a curvature less than that of the hydrated contact lens,characterized in that on the application of pressure upon the annularridge, the material of the curved portion is caused to flex whereby thecurvature (radius) of said curved portion is caused to increase and/orthe diameter of the annular protrusion is caused to increase.

In a sixth aspect of the invention, there is provided a packaged contactlens comprising a blister cup containing a hydrated contact lens ofpre-determined hydrated curvature, a saline solution, and a foil coversealed to a rim of the blister cup, the blister cup comprising anannular ridge (or protrusion) on its interior surface and a curvedoptical portion radially inwards from said annular protrusion saidcurved portion having a curvature less than that of the hydrated contactlens, characterized in that the blister cup comprises a tapered outerportion (or peripheral portion) radially outward from the annular ridge,which tapered outer portions (or peripheral portions) are configured toallow the hydrated contact lens to rest unencumbered in contact with theannular ridge.

In a seventh aspect of the invention, there is provided a contact lensobtainable by the methods defined above.

In an eighth aspect of the invention, there is provided a mould-halfmaster for one or each of a female and a male mould half for use in amethod defined above, from which a respective female or male mould halfmay be cast, and a method of manufacturing a plastic female and/or malecontact lens mould half.

In a ninth aspect of the invention, there is provided a method for thedesign of a contact lens manufacturing process, the method comprising

providing a mould design comprising a first mould half and a secondmould half and therebetween defined a lens-forming mould cavity, thefirst mould half having an optical surface to correspond with a convexsurface of a contact lens, the second mould half having an opticalsurface to correspond with a concave surface of a contact lens, thefirst and second mould halves in unconstrained engagement;

selecting a first material for use in manufacture of a first mould half;

selecting a second material for use in manufacturing a second mouldhalf;

casting a plurality of first and second mould halves each first andsecond mould half pair defining a specific pre-cure mould cavity havingcertain dimensional characteristics;

selecting a lens-forming composition for use in manufacturing a contactlens;

manufacturing a plurality of contact lenses utilizing the plurality offirst and second mould halves according to the mould design, saidmanufacture being according to certain cure and post-cure treatmentconditions;

recording certain lens characteristics; and

devising therefrom an empirical relationship between mould halfdimensions and desired lens characteristics for use in sizing of mouldhalves in a contact lens manufacturing process.

In a tenth aspect, there is provided a process for manufacturing acontact lens having predetermined lens characteristics, the processcomprising selecting a lens-forming composition for use in manufacturingthe contact lens, providing first and second mould halves of dimensionsdetermined according to an empirical relationship determined for thatlens-forming composition by the above method, arranging said mouldhalves in a mould half arrangement defining a pre-cure (lens-forming)mould cavity, disposing the lens-forming composition in the pre-curemould cavity, curing said composition to form a pre-hydrated lens,separating the first and second mould halves and hydrating thepre-hydrated lens to produce a contact lens of pre-determined lenscharacteristics.

ADVANTAGES OF THE INVENTION

The method and articles of the present invention enable a significantlymore efficient manufacturing process for contact lenses and inparticular packaged daily disposable contact lenses. The methods andarticles of the invention enable a contact lens mould half to beutilized as a blister cup in contact lens packaging whilst enhancing theefficiency in terms of procedure and material use in packaged contactlens manufacture. The method and articles of the invention furtherenable the use of a contact lens mould half as a packaged contact lensblister cup which packaged contact lens blister cup remains compact,efficient to manufacture and distribute and reduces handling of themanufactured contact lens.

The method of designing and manufacturing contact lenses according tofurther aspects of the present invention, taking advantage of theunconstrained manner in which the mould halves engage (e.g. ball andsocket arrangement) is significantly more efficient and negates the needfor precision manufacture of peripheral portions of the mould halves (ascompared with prior art piston-cylinder arrangements) and allowsrelatively straightforward accommodation in changes in the manufactureprocess (e.g. different materials or conditions).

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 12 illustrate in cross-section the arrangement of female andmale mould halves according to a preferred embodiment of the presentinvention at various stages of the method of manufacture and use of apackaged contact lens;

FIG. 13 illustrates in cross-section a female mould half of oneembodiment of the present invention.

FIG. 14 illustrates in cross-section a prior art female mould halfoverlain with a hydrated contact lens;

FIG. 15 illustrates a contact lens in cross section and the keydimensions thereof; and

FIG. 16 illustrate in cross-section and in plan three embodiments of afemale mould half/blister cup of the present invention having circular,rectangular and oval shapes.

FIG. 17 illustrates the angle of a return formed on a mould half in apreferred embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides for an improved contact lens manufacturingprocess, a contact lens manufacturing process that is more efficient andallows a mould half to be utilized in a contact lens blister pack, andprovides for an improved contact lens blister in which the lens isreadily retrievable by the user. It further allows for a compactpackaging of contact lenses suitable for efficient distribution, whichminimizes the use of materials in its manufacture. Further, it allowssignificant freedom in design of mould half/blister cup shape andvariation in materials type without the need to significantly change themanufacturing process.

A contact lens manufacturing method of the present invention comprisesproviding two mould halves, a first (concave) mould half which has aconcave mould surface which corresponds with the convex surface of thecontact lens to be formed and a second (convex) mould half which has aconvex mould surface which corresponds with the concave surface of thecontact lens to be formed. By ‘concave mould surface which correspondswith the convex surface of the contact lens’ it is meant not that thecurvature (radius) of the concave mould surface is identical to thecurvature of the convex surface of the hydrated contact lens, or eventhe pre-hydrated contact lens, but that the concave mould surface isresponsible for the shaping of the convex surface of the resulting lens,which has a size and curvature that derives from that of the concavemould surface as a result of the process (which meaning similarlyapplies to ‘convex mould surface’). The mould surfaces of the first andsecond mould halves may each be said to have an optic zone and aperipheral zone. An optic zone of a mould surface or of a mould half asused herein is that part of the mould surface or mould half whichcorresponds with (i.e. which ultimately shapes) the optic zone of a lensto be manufactured in the mould half. By optic zone of a lens, it ismeant that portion of a lens which contributes corrective power to thelens. A peripheral zone of a mould surface or mould half is that part ofthe mould surface half that corresponds with (i.e. which ultimatelyshapes) the peripheral zone of a lens to be manufactured in the mouldhalf. By peripheral zone of a lens, it is meant that portion of a lenswhich is not the optic zone and which is peripheral to the optic zoneand does not substantially contribute corrective power to the lens.

The first mould half may otherwise be referred to as a female mould halfand the second mould half may otherwise be referred to as a male mouldhalf. For the method of the invention, the first and second mould halvesmay be provided in lens-forming engagement, typically by placing thesecond mould half on the first mould half (or vice versa) whereby themould halves define therebetween a pre-cure mould cavity defined inparticular by the first, concave, mould surface and the second, convex,mould surface, wherein a perimeter of the first or second mould surfaceis defined by an annular ridge formed on the respective mould half.

Prior to bringing the mould halves into lens forming engagement, alens-forming composition, e.g. a lens forming fluid composition, whichis curable to form a lens, may be disposed onto a surface of the firstor second mould half so as to effectively dispose the lens-formingcomposition into the pre-cure (lens forming) mould cavity. Typically,the lens-forming composition is charged or disposed into the first mouldhalf (the female mould half), but depending upon the configuration ofapparatus for manufacture and the nature (in particular viscosity) ofthe composition may be disposed onto the female or male mould half.

The composition in the pre-cure mould half may then be cured (e.g. byexposing the mould arrangement to curing conditions, such as heat orultraviolet radiation) to form a pre-hydrated lens. The mould halves maythen be separated.

The method of the invention is characterized by provision of mouldhalves that may flex or adapt relative to one and/or other during curingto accommodate the monomer shrinkage caused during curing (i.e. thevolume reduction associated with curing the lens-forming composition toform the pre-hydrated lens). The mould halves are particularlycharacterized in that at least one and preferably both of the mouldhalves are unconstrained, by which it is preferably meant that there isno dimensional change that is prevented by the nature of the engagementof the mould halves. More preferably, relative movement of the first andsecond mould halves is not prevented. In particular, it is preferredthat engagement between the mould halves is unconstrained, by which itis meant that at least relative radial movement and preferably alsorelative axial movement of the first and second mould halves is notprevented by the manner of engagement of the mould halves. Preferably,such relative radial and axial movement of the optical portions of themould halves, more preferably optic zones of the mould halves, is notprevented by the engagement of the mould halves. Optionally, relativerotational movement (tilting) is at least in part not constrained by theengagement of the mould halves. By not constraining the relative axialmovement of the mould halves, e.g. by not having a rigid shoulder on forexample the female mould half and a corresponding engagement on the malemould half, the mould halves may move together to an extent required.Such movement requires a degree of flexibility in one or other mouldhalf and this flexibility is preferably not provided by a flexible lip(as is known in the prior art) but instead by pliability or flexibilityin the material of the one or both mould halves including a non-rigidridge.

The first and/or second mould halves are further characterized by havingsufficient flexibility or pliability such that during curing of alens-forming composition, the first and/or second mould halves moveand/or flex such as to define between the first and second mouldsurfaces a second, post-cure, mould cavity which defines a smallervolume than the first pre-cure mould cavity.

Preferably, the flexibility is provided in the optical portion of thefirst and/or second mould half (i.e. the optical surface), morepreferably including the optic zone of the first and/or second mouldhalf. The flexibility is preferably provided to the first (female) mouldhalf and optionally and preferably also the male mold half. Morepreferably the flexibility is not discontinuous across the opticalportion of the or each mould half, which preferably includes the opticzone. By ‘not discontinuous flexibility’ it is meant that there are noclear discontinuities in the degree of flexibility across at least theoptical portion of the mould half. That is not to say that flexibilityis constant across the mould half, since it may vary, for example at thecentre as compared with the edges. However, there should be no focus offlexibility or region in which flexibility is restricted. Optionally,the flexibility across the optical portion (i.e. mould surface) of theor each mould half is substantially uniform.

Thus, it is a preferred embodiment that the curvature of the mouldsurface of one, other or both mould halves is, before curing, differentto the curvature of the corresponding surface of the pre-hydrated lensformed and that thus, the said mould surface curvature changes (i.e. isallowed to change) during the curing step. This characteristic ispreferably enabled by the not discontinuous flexibility of the opticalportion of the mould half and/or the unconstrained engagement of themould halves, as discussed above. Such an open and flexible arrangementenables the mould halves during curing to reach a stable configurationwithout forcing constraints on the movements and shapes of the mouldhalves and mould arrangement which can otherwise lead to errors inmanufacture, the requirement for precision manufacture and points ofweakness.

Preferably at least a female mould half is unconstrained in engagementwith the male mould half and is sufficiently pliable or flexible acrossthe optical portion, which flexibility is not discontinuous, that thecurvature of the mould surface thereon may change to accommodate avolumetric reduction of material during curing. More preferably both themale and female mould halves are unconstrained (e.g. they are inunconstrained engagement) and optionally both exhibit the saidflexibility or pliability.

In one embodiment, the mould halves or mould arrangement is such thatthe mould halves move, flex or adapt to define therebetween a second,post-cure, mould cavity, which second post-cure mould cavity defines asmaller diameter than the first pre-cure mould cavity. In particular,according to this embodiment, the diameter of the annular ridge isreduced during the curing step. Without being bound by theory, it isbelieved that the reduction in diameter of the non-rigid annular ridgemay occur due to slight softening and increasing pliability of the mouldmaterial under curing conditions, whereby the volumetric shrinkage ofthe lens-forming composition during curing causes adjustment in whateverdimension there is an inclination for, due to the relative propertiesand shapes of the mould halves and materials used. In this embodiment,this is reduction in annular ridge diameter. It is believed it is theunconstrained nature of the mould arrangement allowed by the moulddesigns according to the present invention that enables the change ofleast resistance to occur in accommodating the volumetric reduction,which change may either be radial contraction of the annular ridge, orradial expansion of the annular ridge (which allows the second, male,mould half to be drawn into the cavity).

In a second embodiment, the mould halves or mould arrangement is suchthat the mould halves move, flex or adapt to define therebetween asecond, post-cure, mould cavity, which second post-cure mould cavitydefines a greater lens diameter (or at least a greater annular ridgediameter) and preferably a greater curvature (greater radius) than saidfirst pre-cure mould cavity. Additionally, or alternatively, accordingto the second embodiment, the mould arrangement or mould halves are suchthat during curing as they tend to be drawn together, at least the firstmould half may flex, due to pressure applied at an annular ridge thereonby the surface of the second mould half, to accommodate the second mouldhalf.

In another aspect and in a preferred embodiment of the aforementionedaspect and embodiments, the invention may be characterized by provisionof mould halves in the form of open flexible cups which are notconfigured in a piston-cylinder slide-fit arrangement and/or whichdefine such an annular ridge which is not rigid. Preferably, the mouldhalves engage in a ball and socket arrangement, the second, male, mouldhalf optical portion being the ball abutting an annular ridge formed onthe first, female, mould half defining the socket.

In each aspect, it is preferred that the male and female mould halvescontact one another only via the annular ridge on one (preferably thefemale) mould half and a corresponding abutment zone on the other(preferably male) mould half. The abutment zone may be defined simply asthat part of a mould half with which the annular ridge of the othermould half makes contact. In the preferred embodiments of the inventionin which the annular ridge is formed on the first (female) mould half,the abutment zone is that part of the convex surface of the second(male) mould half which contacts the annular ridge of the first mouldhalf when the two mould halves are in lens-forming engagement. Theabutment zone may be considered to be the curved surface area between(and including) two line circumferences about the second (male) mouldhalf, a first circumference corresponding to the contiguous annularpoint of contact of the annular ridge with the convex surface of thesecond mould half when the mould halves are in lens-forming engagementprior to curing and a second circumference corresponding to thecontiguous annular point of contact of the annular ridge with the convexsurface of the second mould half after curing (and monomer shrinkage) ofthe lens-forming composition. The first circumference may be smaller orlarger than the second circumference depending upon the relativemovement of the particular mould arrangement during curing. It is aparticularly preferred feature that the abutment zone does not restrict,stop or fix relative movement of the first and second mould halves byproviding a restriction, stop or fix to the annular ridge, and in caseof the aforementioned embodiments that the abutment zone on the malemould half does not comprise a stop or restriction other than itscurvature against the annular ridge on the female mould half. It is mostpreferred that the second mould half does not exhibit any discontinuityin curvature in the region thereof that is may engage with, preferablycontact, the first mould half.

It should be noted that the annular ridge in accordance with thearticles and methods of the present invention is preferably an integralpart of the mould half (preferably female) on which it is formed and ispreferably not capable of flexing entirely independently of the body ofthe mould half (even when it defines a slight return) in order toaccommodate monomer shrinkage as would a flexible lip of the typedescribed in the prior art (GB-A-1575694) (i.e. the annular ridge is nota flexible lip of the type in the prior art).

The methods of the invention further comprise separating the two mouldhalves on completion (or substantially on completion) of curing.Preferably, the mould halves may be separated, in one embodiment whereboth mould halves are formed of the suitably pliable material, byapplying outward lateral pressure to the male mould half (or downwardpressure to flanges formed on the male mould half). The male mould halfmay then be lifted away from the female mould half containing thepre-hydrated lens. Typically, a cured flash ring is withdrawn along withthe male mould half.

In a preferred embodiment of the invention, the male and female mouldhalves of the mould arrangement may be configured in their radiallyoutward portions (i.e. those portions of the male and female mouldhalves radially outward from the annular ridge), or peripheral (ortapered) portions, to have closely matching contours, preferably withouttouching, whereby the amount of materials that is required to make aflash ring is minimal. It is preferable that in accordance with themethod of the invention that excess lens-forming fluid composition isapplied to the lens-forming cavity such that excess fluid is expelledwhen the two mould halves are formed in a sealed lens-formingengagement, the expelled fluid collecting in a flash ring cavity definedby the space between the peripheral portions of the mould halves to forma complete flash ring of fluid. A complete flash ring ensures thatsufficient fluid is provided for lens formation whilst preventing anyatmospheric influences (e.g. oxygen seepage) on the edge portions of thecuring lens.

The first and second mould halves should be placed in sealedlens-forming engagement after disposal of lens-forming composition inthe lens-forming cavity. Preferably the first and second mould halvescontact only between the annular ridge of one (e.g. the first) mouldhalf and abutment zone of the other (e.g. the second) mould half. Thelens-forming engagement should be achieved by applying sufficient forcein bringing the first and second mould halves together (typicallyapplied to the second, male, mould half when placed in the first,female, mould half) to cut the lens-forming composition (e.g. by theforce being greater than applicable surface tension) in order to causethe annular ridge and abutment zone to come into contact and separatelens-forming composition from flash ring composition.

The female mould half according to the present invention and preferablyutilized in the methods of the invention has, as discussed, an annularridge and is sufficiently flexible that under curing conditions (to curea contact lens-forming curable fluid composition) and in contiguouscontact via the annular ridge with a male mould half, the female mouldhalf may flex to at least an extent to accommodate any shrinkage of thecomposition. Preferably, the flexibility of the female mould half foraccommodating shrinkage of lens-forming composition manifests itself inradial expansion or contraction of the annular ridge (i.e. increase ordecrease in diameter of the annular ridge). The female mould halfpreferably has a curved optical portion radially inwards from theannular ridge and, preferably also, a tapered (or peripheral) portionradially outward from the annular ridge. The tapered zone may be definedat its perimeter by a rim, which preferably defines a planesubstantially parallel with that defined by the annular ridge.Preferably, the mould half has a radially extending flange formed on therim of the mould half (preferably extending in the plane defined by thecircumference) so that it may be suspended by resting the flange on theboundary of an aperture (typically a circular aperture sized to receivethe mould half) formed in a receptacle tray, which is preferably used inthe manufacturing process to produce an array of contact lensessimultaneously. It is preferred that the female mould half is generallycup-shaped.

Preferably the annular ridge of the first (female) mould half iscircular and preferably the optical portion of the female mould half(i.e. that portion radially inward from the annular ridge) is circularlysymmetrical. The peripheral portion of the female mould half may be ofany suitable or desirable shape, e.g. square, rectangular,lozenge-shaped, circular, provided that it does not impede the second(male) mould half from engaging with the first mould half inlens-forming engagement (e.g. an optical portion of the second mouldhalf abutting against the annular ridge of the first mould half in aball and socket arrangement). The peripheral portions of the first andfemale mould half need not be of common shape nor designed or configuredfor engagement with each other, but should preferably be configured soas not to prevent or impede engagement of the optical portions of thefirst and second mould halves. Thereby, there is considerable designfreedom, particularly in the peripheral portions of the mouldarrangement. (The optical portion of the male mould half preferably isconfigured for abutment against the annular ridge and the opticalportion is preferably circularly symmetrical).

Preferably both the annular ridge and the rim of the first (female)mould half are circular. Furthermore, it is preferred that at least theoptical portion of the first mould half is circularly symmetrical andpreferably the mould half in its entirety is circularly symmetrical.This is beneficial in enabling the manufacturing process to besimplified and for packing efficiency (when the female mould half isutilized as a blister or a contact lens receptacle in contact lenspackaging).

Preferably, the first mould half (or female mould half) used in themethod of the invention is further characterized, in an embodiment inwhich the annular ridge is formed on the female mould half, by the firstmould surface having a return, typically defined by the annular ridge(e.g. the radially-internal surface thereof), thereby allowing thepre-hydrated lens to be retained in the first mould half upon separationof the mould halves. In this embodiment, the method preferably furthercomprises releasing at least the edges of the pre-hydrated lens from thefirst mould half by applying a pressure to cause radial flexing of theannular ridge. It is particularly advantageous in a female mould halfhaving a concave mould surface in which there is defined a return (e.g.by way of an annular ridge) that the cured, pre-hydrated lens may bereleased from the concave mould surface or at least have its edgesreleased from the portion of the surface defining a return sincehydration is much more predictable, controllable and faster and there isless risk of edge damage or lens inflexion if the edges of thepre-hydrated lens are released prior to hydration. This is of particularimportance for highly automated manufacturing processes where an arrayof lenses may be manufactured at the same time and subject tosimultaneous pre-programmed process steps. Should some lenses in anarray of lenses not properly hydrate or not properly hydrate within theprogrammed time, it can result in inadequate hydration or damage to thelens and thus a reject lens or reject array. It is thus provided in afurther aspect of the present invention a female mould half having anannular ridge and a concave mould surface radially inward thereof, theconcave mould surface to correspond with a convex surface of apre-hydrated lens to be formed therein, wherein the annular ridgedefines a return on the concave mould surface and which annular ridge ormould half is sufficiently flexible that it may be flexed sufficientlyto release the edges of a cured pre-hydrated lens formed against theconcave mould surface.

Preferably the return may be defined by a tangent on the curved surfaceof the concave mould surface where it meets the annular ridge, thetangent having an angle to the plane of the annular ridge of from 10 to80° (an angle of 90° or greater corresponding to their being no returnprovided), preferably from 30° to 60° and most preferably about 45°.Preferably, the return should define a curved surface extending smoothlyfrom the concave surface of the first mould half (although an angledreturn can be provided, in which case the ‘tangent’ referred to shouldbe a line from the widest point to the annular ridge). The extent of thereturn, being the distance from the widest point (corresponding to thediameter of the pre-hydrated contact lens being formed) to the annularridge should be such as to allow the pre-hydrated contact lens to beretained within the first mould half after separation of the mouldhalves, but also to allow the edges of the pre-hydrated lens to bereleased by flexing the first mould half. Ideally, the extent of thereturn is up to 10 μm, preferably in the range 4 to 6 μm.

The method of the invention preferably further comprises subsequentprocess steps carried out within the first (or female) mould half inwhich it is formed. Most preferably, the first (or female) mould half issubsequently utilized as a blister cup for a contact lens package. Thus,the method preferably further comprises hydrating the lens in the firstmould half to form a hydrated lens and, optionally, washing the hydratedlens in the first mould half. The hydration and washing fluid istypically water or a preservative or saline. The method preferablycomprises the further step of providing a quantity of preservative fluid(e.g. saline solution) into the first mould half and applying a sealingfoil to a rim of the first mould half defining an internal volumecontaining the hydrated lens, whereby the first mould half forms ablister cup of a packaged contact lens. It is particularly advantageousto carry out further process steps in the female mould half in which thelens is formed and to utilize the female mould half as a blister cup ina contact lens package since this reduces the amount of contact with thecontact lens and thus the risk of any contact-mediated contamination(albeit that risk is typically small in an efficiently and well-runmanufacturing operation) is minimized and the use of materials isreduced. In particular, normally mould halves are disposed of orrecycled and separate blister cups are manufactured which are typicallydisposed of by the user. By utilizing the mould half as a blister cup,material waste may be minimized.

During the mould arrangement engagement process or curing process atleast one mould half should be unconstrained relative the other.Typically both may be free to move. For example, first (female) mouldhalves are preferably suspended by flanges from the rim thereof in anaperture formed in a tray (apertures preferably being of a size to allowexpansion of mould arrangement during curing if necessary). Preferably,the second (male) mould halves are simply deposited on top and lightlypressed sufficient to cut the lens-forming composition and to causesealed engagement. At least one (and preferably both) of the mouldhalves should be free to float or centre with respect to the other. Aplurality of female mould halves can be formed in a perforated tray withthe male mould halves provided in unconstrained engagement with thefemale mould halves. Preferably however the female mould halves are alsounconstrained and may ultimately be formed in a blister by applicationof a foil to a plurality of mould halves.

According to the present invention, the flexibility of the mouldarrangement whereby the volumetric reduction during curing isaccommodated may be provided by radial flexibility of the first (female)mould half (e.g. including radial contraction or expansion of theannular ridge of the female mould half) and, optionally, diaphragmflattening of the female mould half, contraction of the curved opticalportion of the female mould half or more likely diaphragm expansion ofthe convex mould surface of the second (male) mould half. Preferably,the flexibility of the mould arrangement is provided substantially byradial flexibility and substantially not by diaphragm behavior, by whichit is meant that the volume reduction that is accommodated by theflexibility is no more than 10% attributable to diaphragm behavior andpreferably no more than 5% and most preferably involves no diaphragmbehaviour.

As mentioned above, in the mould arrangement described, the first andsecond mould halves together define a pre-cure cavity and, after curingof the contact-lens forming fluid composition, a post-cure cavity. Inone embodiment according to a first embodiment described above in whichthere is radial contraction of the annular ridge of the female mouldhalf, the post-cure cavity may have an annular ridge with a diameter dof δd less than that of the pre-cure cavity. Preferably, δd is in therange 2 to 200 μm, more preferably from 5 to 100 μm, still morepreferably from 25 to 80 μm and most preferably from 40 to 75 μm. Suchannular ridge diameter (or cavity) contraction would be preferably for atotal diameter of ˜10.5 mm. The percent contraction is preferably in therange 0.1 to 1%, preferably 0.5 to 0.8%. Preferably according to thisembodiment, the concave mould surface and the convex mould surface movediametrically toward one another (e.g. by flattening of the dome of thefirst, female, mould half and/or by doming of the second, male, mouldhalf) thereby reducing the thickness of the pre-cure cavity by from 2 to20%, preferably from 5 to 15% and more preferably about 10%.

In another embodiment in which there is radial expansion of the annularridge of the female mould half (thereby allowing the concave and convexsurfaces to move toward one another), the post-cure cavity may have adiameter d of δd greater than the pre-cure cavity. Preferably, δd is inthe range 2 to 50 μm, more preferably from 3 to 20 μm and still morepreferably at least 5 μm. Preferably, the female mould half as definedherein is capable of flexing under the internal forces induced bymonomer shrinkage during polymerization, such as to increase the annularridge diameter by at least 3 μm, preferably at least 5 μm, optionally atleast 10 μm, more preferably in the range from about 5 μm to about 50 μmand most preferably in the range from about 5 μm to about 20 μm.

The first (female mould half), for use in the method of the inventionand which may be used as a blister cup of a contact lens package,preferably comprises an annular ridge which is not rigid and has radialflexibility which may be defined as allowing an increase in diameter ofthe annular ridge upon application of a force (which is preferably aforce that is within the elastic limit of the mould half, by which it ismeant that on removal of the force, the mould half returned to itsoriginal state). Preferably, the flexibility may be defined as allowingan increase of at least 5 μm when a force of no more than 350 N,preferably no more than 250 N, more preferably no more than 200 N, andstill more preferably no more than 100 N is applied between fixed platenarranged to contact a rim of the mould half and an external base of themould half.

The first (female) mould half should be sufficiently rigid to be selfsupporting and sufficiently rigid to substantially hold its shape duringthe curing phase whilst being flexible enough to accommodate thevolumetric reduction during curing. For example, the first (female)mould half may be defined as having a rigidity whereby at least 10 N,preferably 25 N, force is required to be applied according to the platenarrangement referred to above in order to cause a radial expansion ofthe annular ridge of at least 5 μm.

In the embodiments of the invention described herein in which theannular ridge is formed in the first (female) mould half, there may bedefined a first portion being an optical portion radially inward fromthe annular ridge and a second portion, being a tapered or peripheralportion radially outward from the annular ridge. Preferably, theperipheral portion is configured such as to allow containment of ahydrated lens and to allow the hydrated lens to rest unencumbered incontact with the annular ridge. Where the tapered peripheral portiondefines a curve, it is preferred that the curve has a radius ofcurvature of similar to or greater than the radius of the front curve ofa hydrated lens. Preferably the first, optical, portion defines a curvewith a smaller radius than the curve of the front surface of a hydratedlens and has a smaller diameter than the hydrated lens.

Preferably, the first (female) mould half has a rim (which is preferablysubstantially in a plane parallel to the annular ridge) that defines aninternal volume of the mould half. The female mould half may preferablybe configured (as a female mould half for use in manufacture of a lensand/or as a female mould half used as a blister cup of a contact lenspackage) to possess one or more of the following characteristics:

a) a circularly symmetrical internal volume relative the rim;

b) a curved second portion radially outward from an annular ridge formedon the first mould half, which curved second portion has a radius ofcurvature of 10 mm or less, preferably from 8.5 mm to 9 mm;

c) a curved second portion radially outward from an annular ridge formedon the first mould half, which curved second portion has a radius ofcurvature equal to or within plus or minus 200 μm of the front opticalzone radius for a hydrated −3.00D lens;

d) a ratio of the radius of the rim of the mould half to the lens backoptical zone radius of the hydrated lens is less than 1.2, andpreferably less than 1.1;

e) the maximum internal height of the internal volume from an annularridge formed on the female mould half to the intersection with the rimdiameter is 6 mm or less;

f) the vertical clearance between the lens sagittal height and theinternal height of the internal volume from an annular ridge formed onthe female mould half to the intersection with the rim diameter is 2.5mm or less, preferably 2.2 mm or less or even 2.1 mm or less.

g) the ratio of the maximum internal height of the internal volume froman annular ridge formed on the female mould half to the intersectionwith the rim diameter to the front sagittal height of a hydrated lens is1.6 or less.

h) the diameter of the rim is 18 mm or less and preferably 17 mm orless;

i) the ratio of the diameter of the rim to the diameter of a hydratedlens is 1.4 or less and preferably 1.3 or less, more preferably 1.25 orless and most preferably 1.2 or less.

Optionally any two or more of the above features a) to i) may beprovided and preferably all of features a) to i). By configuring thefemale mould half having these one or more features a) to i), a compactfemale mould half may be achieved, which when utilized also as a blistercup of a contact lens package, is capable of being compactly packaged,minimizes the use (and waste) of material and reduces the likelihood ofa contact lens inverting in the packaging.

The internal volume as defined by the rim of a female mould half ispreferably in the range 0.75 to 1.5 ml, more preferably 0.8 to 1.25 ml,still more preferably 0.8 to 1.1 ml and most preferably 1 ml or less. Inone embodiment, the female mould half has a volume in the range 0.8 to0.9 ml, e.g. about 0.85 ml.

Preferably, a female mould half as described above may be utilized as ablister cup of a contact lens package.

The mould halves may be formed of any suitable material according to thepredictability or consistency of behaviour during moulding andprocessing, the conditions of curing, the nature of the lens-formingfluid composition used in the manufacture of contact lens and therequirements of flexibility as discussed herein. In one embodiment, thefemale mould half is formed of a material capable of providing anecessary degree of flexibility to allow contraction to accommodatemonomer shrinkage or to expand to allow receipt of the male mould halfto satisfy monomer shrinkage during curing. The male mould half may bemade of the same or different material, which may be a different rigidmaterial (e.g. a cast metal mould, glass mould or rigid plastic) but ispreferably the same material as the female mould half. Typically, e.g.for thermal or UV curing (and typical lens-forming material), the mouldhalves may be formed of polyolefins such as polyethylene andpolypropylene, polystyrene, polycarbonate, polymethyl methacrylate, acopolymer of ethylene and vinyl alcohol, polyacetal, polyamide,polyester and polysulfone. Preferably, the mould halves comprise ofpropylene-containing polymers or co-polymers. More preferably, the mouldhalves are formed of or comprise polypropylene.

The contact lens-forming composition may be any suitable composition(e.g. any suitable composition known in the art) capable of being curedto form a contact lens. Preferably, the composition comprises a materialcapable of thermal or UV curing to form a contact lens, preferablythermal curing. The contact-lens forming composition may, for example,be such as to form contact lenses of the silicone hydrogel class ofmaterials, examples of which are known in the contact lens art. Thecontact-lens forming composition may typically comprise a radicallypolymerisable monomer compound, or alternatively a macromer or apre-polymer. Such compounds for radical polymerisation to form a contactlens may be selected, for example, from one or more of vinyl, allyl,acryl and methacryl groups. Example compounds may include methacrylatessuch as alkyl methacrylate, siloxanyl methacrylate, fluoroalkylmethacrylate, hydroxyalkyl methacrylate, polyethyleneglycol methacrylateand polyhydric alcohol methacrylate, derivatives of styrene, andN-vinyllacatm. In one embodiment, the contact lens-forming compositioncomprises polymerisable hydroxyalkyl methacrylate (such as hydroxyethylmethacrylate) monomers (or pre-polymers) optionally in combination withone or more further polymerisable co-monomers, such as vinyl pyrrolodoneor a methacrylic acid. The contact lens-forming composition typicallyfurther includes a polymerization initiator, such as a thermalpolymerization initiator or photopolymerisation initiator and optionallya photosensitizer.

In a further aspect of the invention discussed above, there is provideda packaged contact lens comprising a blister cup containing a hydratedcontact lens of pre-determined hydrated curvature, a preservativesolution, and a foil cover sealed to the rim of the blister cup, theblister cup comprising an annular ridge on its interior surface and acurved optical portion radially inwards from said annular ridge saidcurved optical portion having a curvature less than that of the hydratedcontact lens, characterized in that on the application of a force uponthe annular ridge, the material of the curved optical portion is causedto flex whereby the radius of curvature of said curved optical portionis caused to increase and/or the diameter of the annular ridge is causedto increase.

In a still further aspect, there is provided a packaged contact lenscomprising a blister cup containing a hydrated contact lens ofpre-determined hydrated curvature, a preservative solution, and a foilcover sealed to the rim of the blister cup, the blister cup comprisingan annular ridge on its interior surface and a curved optical portionradially inwards from said annular ridge said curved optical portionhaving a radius of curvature less than that of the hydrated contactlens, characterized in that the blister cup comprises a peripheralportion that comprises a shallow taper whereby the contact lens may restunencumbered on the annular ridge. Preferably, the peripheral portion iscurved and the curved peripheral portion defines a curvature greaterthan that of the curved optical portion.

The packaged contact lens preferably comprises a blister cup havingsubstantially similar characteristics to a female mould half asdescribed in detail above and, preferably, the described flexibilitythereof. More preferably, the packaged contact lens comprises a blistercup which is a mould half used in manufacturing of the contact lens.

The packaged contact lens is preferably formed as an array. Optionally,the array may comprise a plurality of blister cups formed on a single(optionally perforated) foil sheet sealed to rims defining the internalvolume of the blister cups. The array of packaged contact lenses ispreferably arranged such as to allow two arrays of packaged contactlenses to be packed blister-to-blister such that the respective foilsare separated by up to 15 mm, preferably up to 12 mm, more preferably inthe range 5 to 10 mm and most preferably up to 8 mm. Optionally, thearray of packaged contact lens is configured, with preferred circularrimmed blister cups, such that the separation between adjacent blistercups in an array is in the range 2-6 mm.

In a preferred embodiment, an array of packaged contact lenses comprisesan array of 3 by 5 lenses or an array of 4 by 4 lenses, whereby amonthly supply of daily disposables may be packaged and dispatched asfour foils (e.g. in packs of two foils) or as required by the user.

In a further aspect of the invention described above, is a method forthe design of a contact lens manufacturing process, the methodcomprising providing a mould design comprising a first mould half and asecond mould half and therebetween defined a lens-forming mould cavity,the first mould half having an optical surface to correspond with aconvex surface of a contact lens, the second mould half having anoptical surface to correspond with a concave surface of a contact lens,the first and second mould halves in unconstrained engagement; selectinga first material for use in manufacture of a first mould half; selectinga second material for use in manufacturing a second mould half; castinga plurality of first and second mould halves each first and second mouldhalf pair defining a specific lens-forming mould cavity having certaindimensional characteristics; selecting a lens-forming composition foruse in manufacturing a contact lens; manufacturing a plurality ofcontact lenses utilizing the plurality of first and second mould halvesaccording to the mould design, said manufacture being according tocertain cure and post-cure treatment conditions; recording certain lenscharacteristics; and devising therefrom an empirical relationshipbetween mould half dimensions and desired lens characteristics for usein sizing of mould halves in a contact lens manufacturing process.

A contact lens having predetermined lens characteristics may then bemanufactured by selecting a lens-forming composition for use inmanufacturing the contact lens, providing first and second mould halvesof dimensions determined according to an empirical relationshipdetermined for that lens-forming composition by the above method,arranging said mould halves in a mould half arrangement defining alens-forming cavity, disposing the lens-forming composition in thelens-forming cavity, curing said composition to form a pre-hydratedlens, separating the first and second mould halves and hydrating thepre-hydrated lens to produce a contact lens of pre-determined lenscharacteristics.

In a still further aspect of the invention is a method of designing acontact lens manufacturing method, which comprises selecting a contactlens mould size according to a desired optical strength and desireddiameter of contact lens, the method comprising selecting a desiredoptical strength and diameter of contact lens, selecting a material fromwhich to form the contact lens and according to pre-determinedvolumetric reduction during curing of that material selecting a contactlens mould of a size and material to account for the pre-determinedvolumetric reduction for the lens-forming material, the size of saidcontact lens mould being determined according to the predeterminedtolerances and flexibility of the mould. According to this method, acontact lens manufacturing process is established by working back fromallowed tolerances in the materials to be used to form the contact lensand the materials to be used to form the mould halves according toproposed curing conditions, e.g. in performing a method of manufacturinga contact lens as hereinbefore defined, rather than imposing restraintson the manufacture of contact lenses and materials and configurations ofmould halves.

The method further comprises, for each type of contact-lens formingmaterial and each type of mould material, establishing a set ofexperimentally determined tolerances which may be applied to designselection.

Accordingly, greater freedom in contact lens manufacturing processes areafforded and less complex manufacturing processes may be achieved(without the need to build in limitations and restraints). Thus asimpler mould cast design may be achieved—the open dish (with non-rigidannular ridge) as described above. This is a fundamentally novelapproach to contact lens mould design with the object of meeting therequirements.

By utilizing the mould arrangement described herein, which has an open(or ball and socket) arrangement in which the mould halves areunconstrained (as compared for example with prior art piston-cylinderarrangements) and therefore have peripheral portions that do not requireprecision manufacture, the physical effect of changes in materials orconditions can be readily accounted for simply by allowing physicalproperties resulting from material or process changes to be accommodatedin the manufacturing process by establishing an empirical relationshipas described above, for example. Since the peripheral portions are notsubject to particular constraint and the operation of the process notreliant on precise manufacturing to meet such particular constraints,changes in materials, process or design can be readily accommodated.Thus, the mould halves and manufacturing methods of the presentinvention allow a significant degree of design freedom, such as theselection of lens diameter, hydration, lens material, mould material,curing conditions without significantly adjusting the manufacturingprocess, but simply by establishing a deviation factor to be accountedfor when sizing the mould half master.

The invention will now be described in more detail, without limitation,with reference to the accompanying Figures.

In FIG. 1, a contact lens mould arrangement 1 comprises a first, female,mould half 3 and second male mould half 5 configured for engagement toform between a convex surface 7 of the male mould half 5 and a concavesurface 9 of the female mould half 3, a first pre-cure mould cavity(shown in FIG. 2), the perimeter of which is defined by an annular ridge13 formed on the female mould half 3, which is designed to not preventflexibility of the lens half (i.e. is not rigid).

The female mould half is preferably provided with a narrow collar orflange 15 to allow the mould arrangement 1 to rest in an array supportedonly by the collar 15 thereby allowing free relative movement of themould halves during manufacture.

A lens-forming composition 17 (typically comprising a polymerisablemonomer) is charged into the female mould half 3 in an amount slightlymore than sufficient to fill the first pre-cure mould cavity 11 wherebyexcess composition 17 is displaced into flash-ring cavity 19 when themould halves are brought into lens-forming engagement as in FIG. 2.

The mould halves may then be left to self-align during curing or mayfirst be simply aligned by applying a slight plate pressure (parallelwith the flat surface of narrow collar 15) to the top of the male mouldhalves, which alignment step may be assisted by the provision of anarrow collar 21 on the male mould halves 5 which corresponds with thenarrow collar 15 of the female mould halves 3. Preferably, an array ofsuch mould arrangements is provided and a single plate alignment stepcan be carried out. Such alignment pressure should be sufficient toensure that the collars are parallel and sufficient to cause the annularridge to contact the abutment zone of the male mould half therebyseparating the ‘wet flash ring’ from the ‘wet lens’ (i.e. cutting thelens-forming composition).

Preferably, the only point of contact between the female mould half 3and the male mould half 5 is line contact between the annular ridge 13on the female mould half 3 against the convex surface 7 of the malemould half. The mould halves are formed of a flexible material whichallows contraction or expansion of the mould halves (e.g. lateral orradial expansion or contraction of the annular ridge 13 under curingconditions). In addition, for example, under applied pressure againstthe annular ridge 13 the female mould half 3 may be caused to flexlaterally (thereby increasing the diameter of the annular ridge 13 andflattening the curvature of the concave surface 7). Optionally, the malemould half may also be capable of some flexibility (lateral contraction)whereby the curvature of the convex surface is increased and optionally,but less preferred, some diaphragming may occur.

The composition 17 is then cured by application of heat (where thecomposition is heat curable) or UV light (where the composition is UVcurable), for example. During curing, the inevitable reduction in volumeof the composition 17 (monomer shrinkage) has the effect of an appliedpressure on the mould arrangement. The pressure causes the allowedflexibility of the female mould half 3 and optionally the male mouldhalf 5 to adapt thereby accommodating the reduction in volume ofcomposition 17 during curing.

As can be seen in FIG. 4, a pre-cure mould arrangement 23 is shown alongwith a post-cure mould arrangement 25. As can be seen, a post-cure mouldcavity 27 is defined and contains a cured hard lens, whilst a curedflash ring 29 is formed in the flash ring cavity 19. The post-cure mouldcavity 27 has a post-cure diameter 31 (i.e. the diameter of the hardlens formed and the diameter of the annular ridge 13 in the post-curearrangement 25), which may be designated d′, that is smaller by anamount δd than the pre-cure diameter 33 (i.e. the diameter of thepre-cure mould cavity and the annular ridge 13 before the cure process),which may be designated d. Further, the post-cure lens thickness 35,which may be designated t′, is less than the pre-cured cavity thickness37, by an amount δt. Accordingly, in order to obtain a hard cured lenshaving a certain radius of curvature (back and front), thickness andlens diameter, male and female mould halves 3,5 are selected that havecorresponding curvatures, annular ridge diameter and in lens formingengagement a pre-cure cavity thickness that respectively account for thechanges that are allowed to occur by the unconstrained arrangementduring curing.

The mould halves may be separated by applying pressure to the collar 21of the male mould half 5 (until an audible ‘crack’ occurs). On removalof the male mould half 5, the cured flash ring 29 may separate with themale mould half 5 (due to differences in surface properties between themale mould half 5 and the female mould half 3 or to differences inpressure applied to the flash ring, which upon release may effectivelybe gripped by the male mould half 5) or be independently removed. Areturn 39 (shown in FIG. 5) may be provided on the female mould half 3in association with the annular ridge 13, which has the benefit of amore rounded front edge of the lens formed (for better comfort in theeye of the wearer) and the further benefit that on separation of themale mould half 5, the cured pre-hydrated lens 41 remains with thefemale mould half 3.

In order to hydrate the pre-hydrated lens 41, it is preferred to firstrelease the lens from the optical zone 43 of the female mould half 3(since hydration is quicker, more consistent and less likely to causedamage to the edges of the lens if it is allowed to occur through theedges and both surfaces of the lens rather than simply through the backsurface of the lens). Accordingly, the separated female mould half 3containing the pre-hydrated lens 41 may be flexed laterally (see FIG. 6)by, e.g. applying pressure using a frusto-conical insert 45 shaped toapply pressure to the perimeter 47 of the female mould half 3 causingthe edges of the pre-hydrated lens to be released from the return 39formed in the optical surface 9 of the female mould half 3, as shown inFIG. 7.

FIG. 8 shows a hydrated lens 49 in a hydration liquid 51, which ispreferably water, in the female mould half 3. The pre-hydrated lens 41may have expanded by 25 to 50% (depending upon the lens materialselected) during hydration. The diameter of the hydrated lens 49 is thuslarger than that of the pre-hydrated lens 41 and of the annular ridge 13and therefore extends into a volume of the female mould half 3 that maybe referred to as a tapered or peripheral portion 53 since it tapersfrom the optical portion 43 to the perimeter 47. The peripheral portion53 should be so configured (i.e. tapered or curved) to allow containmentof the hydrated lens 49 and to allow the hydrated lens 49 to restunencumbered in contact with the annular ridge 13, which has the benefitof maintaining separation between the lens 49 and the mould surface.Since the hydration liquid 51 may contain unpolymerised ‘residuals’extracted from the pre-hydrated lens 41 and the optical portion 43 ofthe female mould half 3, the hydration liquid must be removed prior tothe addition of the packing solution 52 (see FIG. 9)

FIG. 9 shows the hydrated lens 49 in a packing fluid 52, which can besaline or any comfort enhancing fluid compatible with the physiology ofthe human eye, and the mould half 3 provided with a foil lid 55 attachedto the narrow collar of the female mould half 3, in which the femalemould half 3 is being used as a blister for a contact lens package 57.This assembly is typically sterilized by autoclaving or some othersterilizing process. As mentioned above, this female mould half 3utilised as a blister of a contact lens package 57 is characterized byhaving an optical portion 43 having an optical concave surface 9 of asize and curvature selected to provide through the curing processdescribed a pre-determined size and curvature of pre-hydrated contactlens 41 which corresponds to a desired size and curvature of a hydratedcontact lens 49 and a tapered or peripheral portion 53 which tapersradially outward from the annular ridge 13 in a shallow angle or curveto allow the hydrated lens 49 to rest on the annular ridge 13. That is,the angle or curve of the peripheral portion 53 should be shallower thanthe curve of the parts of the lens occupying that region (i.e. themid-periphery or periphery of the hydrated lens 49). This is as distinctfrom prior art arrangements where the female mould half is proposed foruse as a blister for a contact lens package—for example, WO-A-87/04390which is shown in FIG. 14 has a rigid shoulder 61 (for preventingflexibility and in particular radial flexibility or expansion) and has atapered portion 63 which tapers steeply away from the optical portion 65in a manner that would not allow a contact lens to rest in the base ofthe blister and would require a blister of substantially greater volume.FIG. 13 illustrates in more detail the shallow taper in the peripheralportion 53 of the invention.

FIG. 10 shows an opened blister 59 (i.e. female mould half 3) with theuser's finger 61 contacting the back surface of the hydrated lens 49.Due to separation of the hydrated lens from the curve of the package byresting on the annular ridge 13, the contact lens 49 readily adheres(preferably) to the finger and allows the lens 49 to be removed from theblister 59 (as illustrated in FIGS. 10-12). Downward pressure of thesoft tip of the finger 61 does not result in any damage to the soft lens49 by the annular ridge 13 since there is a retained ‘pool’ of packagingliquid in the optical portion cavity, which pool of liquid preventsdownward pressure of the lens 49 against the annular ridge. The pool ofliquid also ensures preferential adhesion of the wet lens to the fingertip 61 and enhances removal of the lens 49 by the user.

FIG. 15 shows a lens 49 and the dimensions related to it. In particular,the lens back optical zone 67, lens diameter 69, the front sagittalheight 71 and the lens radius 73.

In FIG. 16 is shown in cross section and plan three profiles of femalemould halves/blister cups that may be used in accordance with thepresent invention. Respectively a circular mould half 75, rectangularmould half 77 and oval shaped mould half 79 are shown beneath theircross-sectional profiles. Each has an optical portion 43 which iscircularly symmetrical and defined by an annular ridge 13. Theperipheral portion 53 may be of any suitable shape to allow a second,male, mould half to engage in sealed lens-forming engagement against theannular ridge 13. Respective peripheral portions 53 are defined by acircular rim 81, rectangular rim 83 and oval rim 85, each provided witha flange 87, 89, 91. Accordingly, the shape of the peripheral portion 53of the mould half/blister cup is not critical to the lens-forming stepand need not be manufactured for precision piston-cylinder fit withanother part, thereby enabling freedom of design of the mould halfaccording to the requirements/desires of a blister cup.

In FIG. 17, the return 39 of FIG. 5 is shown in more detail. The curvedsurface of the concave mould surface 93 of the female mould half meetsthe peripheral portion surface 95 at the annular ridge 13. A tangent 97to the curved surface 93 at the ridge 13 forms an angle a with the plane99 of the annular ridge. An angle a of less than 90° defines a return.Preferably, α is in the range 10 to 80°.

EXAMPLE Example 1

A pre-hydrated contact lens is formed using the method of the presentinvention by disposing a quantity of lens-forming composition(comprising hydroxyethyl methacrylate and vinyl pyrrolidone) in alens-forming cavity formed between male and female mould halves (ofpolypropylene) of the invention, in accordance with FIG. 1, andthermally curing the composition. The diameters of the pre-cure mouldcavity, post-cure mould cavity and dry lens formed were recorded and arepresented in Table 1.

TABLE 1 Pre-cure mould Post-cure mould cavity diameter/ cavity diameter/Pre-hydrated lens Moulding No. mm mm diameter/mm 1 10.5879 10.551810.553 2 10.5954 10.496 10.517 3 10.5658 10.5222 10.527 4 10.5846 10.54910.549 5 10.5864 10.5078 10.54 6 10.5626 10.49 10.53 Mean 10.580510.5195 10.5360 STDEV 0.0132 0.0264 0.0138

The mean change in diameter of mould cavity is a 60 μm reduction, whichis a 0.58% contraction on a 10.58 mm aperture. This resulted inapproximately 10% volume reduction.

The free and flexible mould arrangement of the present invention iscapable of flexing or adapting to accommodate the volume reduction dueto curing.

Example 2

As discussed above, a particular characterization of the manufacturingmethod, the female mould half 3 and the blister 59 of the presentinvention is the flexibility of at least the female mould half tolateral flexibility or radial extension. It is preferable that at leastthe female mould half it is sufficiently flexible that a return may beconfigured in the optical surface of the female mould half, associatedwith the annular ridge, whilst enabling the cured pre-hydrated lens tobe released.

The following sets out the deformation under varying loads for a femalemould half formed according to a preferred embodiment of the presentinvention.

A female mould half according to a preferred embodiment was placedbetween fixed and moving platens. Force was therefore applied equally inone direction against the narrow collar 15 of the mould half 3 and inthe other direction against the external surface of the domed opticalzone 43 of the mould half 3.

When compressive Forces of 0, 50, 100 and 200 N were applied, changes inthe diameter (Δd) were recorded. The results are set out in Table 2.

TABLE 2 Diameter Force F/N (d)/mm Δd/μm 0 10 0 50 10.005 5 100 10.021 21200 10.031 31

As can be seen from the data in Table 2, the diameter of the annularridge increases with increasing pressure applied to the female mouldhalf 3 illustrating that the mould half is flexible and that the annularridge is flexible under a load and not rigid. It has been found that anincrease in diameter of the annular ridge of 5 microns is sufficient torelease from the return in the female mould half the edges of thepre-hydrated lens whereby uniform and efficient lens hydration step canbe carried out in situ.

The invention has been described with reference to a preferredembodiment. However, it will be appreciated that variations andmodifications can be effected by a person of ordinary skill in the artwithout departing from the scope of the invention.

1. A method for the manufacture of a contact lens, the method comprisingproviding a first, concave, mould-half having a first concave mouldsurface to correspond with a convex surface of the contact lens;providing a second, convex, mould-half having a second convex mouldsurface to correspond with a concave surface of the contact lens, saidsecond mould half configured to engage with the first mould-half todefine a first, pre-cure, mould cavity therebetween, which mould cavityis defined by the first, concave, mould surface and second, convex,mould surface said first and second mould surfaces having respectivecurvatures to correspond with a pre-determined lens power/curvature andwherein the first or second mould surface is defined by an annular ridgeformed on the respective mould half; disposing into the mould cavity acurable lens-forming fluid composition; curing said composition to forma pre-hydrated lens; and separating the first and second mould halves,characterized in that the engagement between the mould halves isunconstrained and at least one mould half is sufficiently pliable orflexible such that during the curing of said composition the firstand/or second mould halves move relative to one another and/or flex suchas to define between the first and second mould surfaces a second,post-cure, mould cavity, which second post-cure mould cavity defines asmaller volume than said first pre-cure mould cavity and whereby duringcuring the curvatures of the first and/or second mould surfaces areallowed to change.
 2. A method as claimed in claim 1, wherein the firstand/or second mould halves exhibit no discontinuity in flexibilityacross the corresponding first and/or second mould surface.
 3. A methodas claimed in claim 1 or claim 2, wherein, prior to curing, the firstand/or second mould surfaces have a different curvature to thecorresponding surface of the pre-hydrated contact lens formed.
 4. Amethod as claimed in any one of claims 1 to 3, characterized in that atleast the first mould half is formed of a material sufficiently pliableunder curing conditions that during curing, the radial dimension definedby the diameter of the annular ridge changes to accommodate thevolumetric reduction of lens-forming composition due to curing.
 5. Amethod as claimed in any one of the preceding claims, wherein the onlycontact between the first and second mould halves is at the lenscavity-defining circumference, whereby the annular ridge abuts thesurface of the opposing mould half.
 6. A method as claimed in any one ofthe preceding claims, wherein the annular ridge is formed on the firstmould half.
 7. A method as claimed in claim 6, which is furthercharacterized in that the first mould surface defines a return, therebyallowing the pre-hydrated lens to be retained in the first mould halfupon separation of the mould halves.
 8. A method as claimed in claim 7,which further comprises releasing at least the edges of the pre-hydratedlens from the first mould half by applying a pressure to cause radialflexing of the annular ridge.
 9. A method as claimed in any one of thepreceding claim, which further comprises hydrating the lens in the firstmould half to form a hydrated lens and, optionally, washing the hydratedlens in the first mould half.
 10. A method as claimed in claim 9, whichfurther comprises providing a quantity of preservative fluid into thefirst mould half and applying a sealing foil to a rim of the first mouldhalf defining an internal volume containing the hydrated lens, wherebythe first mould half forms a blister cup of a packaged contact lens. 11.A method as claimed in any one of the preceding claims, wherein thefirst and second mould halves together define a pre-cure cavity and,after curing of the contact-lens forming fluid composition, a post-curecavity, wherein the post-cure cavity has a diameter of δd less than thepre-cure cavity, δd being 3-100 μm.
 12. A method as claimed in any oneof the preceding claims, wherein the annular ridge is formed on thefirst mould half and is sufficiently pliable to radially contract undercuring conditions whereby volumetric shrinkage is accommodated.
 13. Amethod as claimed in any one of the preceding claims, wherein theannular ridge is formed on the first mould half and has a radialflexibility defined as allowing an increase in the diameter of theannular ridge of at least 5 μm when a force of no more than 200 N isapplied between fixed platen arranged to contact a rim of the mould halfand the base of the mould half.
 14. A method as claimed in any one ofthe preceding claims, wherein the annular ridge is formed in the firstmould half and there is defined a first portion being an optical portionradially inward from the annular ridge and a second portion, being aperipheral portion radially outward from the annular ridge, wherein theperipheral portion is configured such as to allow containment of ahydrated lens and to allow the hydrated lens to rest unencumbered incontact with the annular ridge.
 15. A method as claimed in claim 14,wherein the second portion defines a curve with similar or greaterradius than a hydrated lens and the first portion defines a curve with asmaller radius than a hydrated lens and has a smaller diameter than thehydrated lens.
 16. A method as claimed in any one of the precedingclaims, wherein the first mould half has a rim that defines an internalvolume of the mould half and possesses one or more of the followingcharacteristics: a) a circularly symmetrical internal volume relativethe rim; b) a curved second portion radially outward from an annularridge formed on the first mould half, which curved second portion has aradius of curvature of 10 mm or less, preferably from 8.5 mm to 9 mm; c)a curved second portion radially outward from an annular ridge formed onthe first mould half, which curved second portion has a radius ofcurvature equal to or within plus or minus 200 μm of the front opticalzone radius for a hydrated −3.00D lens; d) a ratio of a radius of afirst mould half to the lens back optical zone radius of the hydratedlens is less than 1.2, and preferably less than 1.1; e) the maximuminternal height of the internal volume from an annular ridge formed onthe female mould half to the intersection with the rim diameter is 6 mmor less; f) the vertical clearance between the lens sagittal height andthe internal height of the internal volume from an annular ridge formedon the female mould half to the intersection with the rim diameter is2.5 mm or less, preferably 2.2 mm or less or even 2.1 mm or less. g) theratio of the maximum internal height of the internal volume from anannular ridge formed on the female mould half to the intersection withthe rim diameter to the front sagittal height of a hydrated lens is 1.6or less. h) the diameter of the rim is 18 mm or less and preferably 17mm or less; i) the ratio of the diameter of the rim to the diameter of ahydrated lens is 1.4 or less and preferably 1.3 or less, more preferably1.25 or less and most preferably 1.2 or less.
 17. A female mould half asdefined as a first mould half in any one of claims 1 to 16, the femalemould half having an annular ridge, which is sufficiently flexible thatunder curing conditions and in contiguous contact via the annular ridgewith a male mould half, the female mould half may flex to accommodateany shrinkage of lens-forming monomer composition during curing.
 18. Afemale mould half as defined as a first mould half in any one of claims1 to 16, the female mould half having an annular ridge and a concavemould surface radially inward thereof, the concave mould surface tocorrespond with a convex surface of a pre-hydrated lens to be formedtherein, wherein the annular ridge defines a return on the concave mouldsurface and which annular ridge is sufficiently flexible that it may beflexed sufficiently to release the edges of a cured pre-hydrated lensformed against the concave mould surface.
 19. A female mould half asclaimed in claim 18, wherein the return is defined by an angle of atangent to the curve of the concave mould surface as it meets theannular ridge to the plane of the annular ridge in the range of from 10°to 80°.
 20. A female mould half as claimed in any one of claims 17 to19, wherein the annular ridge may radially contract by an amount from 3to 100 μm under curing conditions and/or extend by an amount from about3 to 20 μm under applied pressure in order to release a curedpre-hydrated lens formed in said female mould half.
 21. A female mouldhalf as claimed in any one of claims 17 to 20, wherein the annular ridgehas a radial flexibility defined as allowing an increase in the diameterof the annular ridge of at least 50 μm when a force of no more than 200N is applied between fixed platen arranged to contact a rim of the mouldhalf and the base of the mould half.
 22. Use of a female mould halfaccording to any one of claims 17 to 21 as a blister cup for a contactlens package.
 23. A packaged contact lens comprising a blister cupcontaining a hydrated contact lens of pre-determined hydrated curvature,a preservative solution, and a foil cover sealed to the rim of theblister cup, the blister cup being the first mould-half or a femalemould half as defined in any one of claims 1 to 21 and comprising anannular ridge on its interior surface and a curved optical portionradially inwards from said annular ridge said curved optical portionhaving a curvature less than that of the hydrated contact lens,characterized in that on the application of a force upon the annularridge, the material of the curved optical portion is caused to flexwhereby the radius of curvature of said curved optical portion is causedto increase and/or the diameter of the annular ridge is caused toincrease.
 24. A packaged contact lens as claimed in claim 23, whereinupon the application of a force of up to 250 N by platen between thebase of the blister cup and a perimeter rim of the blister cup theannular ridge extends radially by an amount of at least 3 μm.
 25. Apackaged contact lens comprising a blister cup containing a hydratedcontact lens of pre-determined hydrated curvature, a preservativesolution, and a foil cover sealed to the rim of the blister cup, theblister cup being the first mould-half or a female mould half as definedin any one of claims 1 to 21 and comprising an annular ridge on itsinterior surface and a curved optical portion radially inwards from saidannular ridge said curved optical portion having a radius of curvatureless than that of the hydrated contact lens, characterized in that theblister cup comprises a curved peripheral portion radially outward fromthe annular ridge, which curved peripheral portions together define acurvature greater than that of the curved optical portion.
 26. Apackaged contact lens as claimed in any one of claims 23 to 25, whereinthe blister cup is a mould half as used in manufacturing of the contactlens.
 27. An array of packaged contact lenses comprising packagedcontact lenses as defined in any one of claim 23 to 26, characterized byhaving a common foil sealed to an array of packed blister cups
 28. Anarray of packaged contact lenses as claimed in claim 27, wherein thepackaged contact lenses are arranged and configured to allow twoblister-to-blister arranged arrays to be close-packed whereby thefoil-to-foil distance is no greater than 15 mm, preferably up to 12 mm,more preferably in the range 5 to 10 mm and most preferably up to 8 mm.29. A contact lens obtainable by the method of any one of claims 1 to16.
 30. A master mould for casting a first mould half or a female mouldhalf as defined in any one of claims 1 to 21
 31. A method of designing acontact lens manufacturing process, which method comprises providing amould design comprising a first mould half and a second mould half andtherebetween defined a lens-forming mould cavity, the first mould halfhaving an optical surface to correspond with a convex surface of acontact lens, the second mould half having an optical surface tocorrespond with a concave surface of a contact lens, the first andsecond mould halves in unconstrained engagement; selecting a firstmaterial for use in manufacture of a first mould half; selecting asecond material for use in manufacturing a second mould half; casting aplurality of first and second mould halves each first and second mouldhalf pair defining a specific pre-cure mould cavity having certaindimensional characteristics; selecting a lens-forming composition foruse in manufacturing a contact lens; manufacturing a plurality ofcontact lenses utilizing the plurality of first and second mould halvesaccording to the mould design, said manufacture being according tocertain cure and post-cure treatment conditions; recording certain lenscharacteristics; and devising therefrom an empirical relationshipbetween mould half dimensions and desired lens characteristics for usein sizing of mould halves in a contact lens manufacturing process.
 32. Aprocess for manufacturing a contact lens having predetermined lenscharacteristics, the process comprising selecting a lens-formingcomposition for use in manufacturing the contact lens, providing firstand second mould halves of dimensions determined according to anempirical relationship determined for that lens-forming composition bythe method of claim 31, arranging said mould halves in a mould halfarrangement defining a pre-cure (lens-forming) mould cavity, disposingthe lens-forming composition in the pre-cure mould cavity, curing saidcomposition to form a pre-hydrated lens, separating the first and secondmould halves and hydrating the pre-hydrated lens to produce a contactlens of pre-determined lens characteristics.
 33. A method for themanufacture of a contact lens, the method comprising providing a first,concave, mould-half having a first concave mould surface to correspondwith a convex surface of the contact lens; providing a second, convex,mould-half having a second convex mould surface to correspond with aconcave surface of the contact lens, said second mould half configuredto engage with the first mould-half to define a first, pre-cure, mouldcavity therebetween, which mould cavity is defined by the first,concave, mould surface and second, convex, mould surface said first andsecond mould surfaces having respective curvatures to correspond with apre-determined lens power/curvature and wherein the first or secondmould surface is defined by an annular ridge formed on the respectivemould half; disposing into the mould cavity a curable lens-forming fluidcomposition; curing said composition to form a pre-hydrated lens; andseparating the first and second mould halves, characterized in that atleast the first mould half is formed of a material sufficiently pliableunder curing conditions that during curing, the radial dimension definedby the diameter of the annular ridge changes to accommodate thevolumetric reduction of lens-forming composition due to curing.
 34. Amethod as claimed in claim 33 which is as further defined as in claims 2to
 16. 35. A female mould half having an annular ridge, which issufficiently flexible that under curing conditions and in contiguouscontact via the annular ridge with a male mould half, the female mouldhalf may flex to accommodate any shrinkage of lens-forming monomercomposition during curing.
 36. A female mould half having an annularridge and a concave mould surface radially inward thereof, the concavemould surface to correspond with a convex surface of a pre-hydrated lensto be formed therein, wherein the annular ridge defines a return on theconcave mould surface and which annular ridge is sufficiently flexiblethat it may be flexed sufficiently to release the edges of a curedpre-hydrated lens formed against the concave mould surface.
 37. A femalemould half as claimed in claim 36, wherein the return is defined by anangle of a tangent to the curve of the concave mould surface as it meetsthe annular ridge to the plane of the annular ridge in the range of from10° to 80°.
 38. A female mould half as claimed in any one of claims 35to 37, wherein the annular ridge may radially contract by an amount from3 to 100 μm under curing conditions and/or extend by an amount fromabout 3 to 20 μm under applied pressure in order to release a curedpre-hydrated lens formed in said female mould half
 39. A female mouldhalf as claimed in any one of claims 35 to 38, wherein the annular ridgehas a radial flexibility defined as allowing an increase in the diameterof the annular ridge of at least 50 μm when a force of no more than 200N is applied between fixed platen arranged to contact a rim of the mouldhalf and the base of the mould half.
 40. A female mould half as claimedin any one of 35 to 39, which may be as further defined, as a firstmould half, in any one of claims 1 to
 16. 41. Use of a female mould halfaccording to any one of claims 35 to 40 as a blister cup for a contactlens package.
 42. A packaged contact lens comprising a blister cupcontaining a hydrated contact lens of pre-determined hydrated curvature,a preservative solution, and a foil cover sealed to the rim of theblister cup, the blister cup comprising an annular ridge on its interiorsurface and a curved optical portion radially inwards from said annularridge said curved optical portion having a curvature less than that ofthe hydrated contact lens, characterized in that on the application of aforce upon the annular ridge, the material of the curved optical portionis caused to flex whereby the radius of curvature of said curved opticalportion is caused to increase and/or the diameter of the annular ridgeis caused to increase.
 43. A packaged contact lens as claimed in claim42, wherein upon the application of a force of up to 250 N by platenbetween the base of the blister cup and a perimeter rim of the blistercup the annular ridge extends radially by an amount of at least 3 μm.44. A packaged contact lens comprising a blister cup containing ahydrated contact lens of pre-determined hydrated curvature, apreservative solution, and a foil cover sealed to the rim of the blistercup, the blister cup comprising an annular ridge on its interior surfaceand a curved optical portion radially inwards from said annular ridgesaid curved optical portion having a radius of curvature less than thatof the hydrated contact lens, characterized in that the blister cupcomprises a curved peripheral portion radially outward from the annularridge, which curved peripheral portions together define a curvaturegreater than that of the curved optical portion.
 45. A packaged contactlens as claimed in any one of claims 42 to 44, wherein the blister cupis as further defined as a first mould-half or a female mould half inany one of claims 1 to
 21. 46. A packaged contact lens as claimed in anyone of claims 42 to 45, wherein the blister cup is a mould half as usedin manufacturing of the contact lens.
 47. A mould half or a packagedcontact lens substantially hereinbefore described with reference to thedrawings.